High vacuum process and apparatus



K. c. D. HICKMAN HI GH VACUUM PROCESS AND APPARATUS se lz, 1944. l

Filed Feb. 24. 1943 FIG. 3.

IN VENTOR m M KENNETH C. D. HICKMAN BY WW cv ATTORNEYS- iiEiiiii:

Patented Sept.

HIGH VACUUM PROCESS AND APPARATUS Kenneth C. D. Hickman, Rochester, N. 1., as-

signor to Distillation Products, Inc., Rochester, N. Y., a corporation of Delaware Application February 24, 1943, Serial No. 476,933

15 Claims.

This invention. relates to improved equipment for the production of high vacua,v also to improved process of high vacuumproduction.

The conventional way of producing a high vacuum is by means of a condensation pump. The condensation pump has been improved considerably in the past thirty years; it has also increased somewhat in size. However,, the condensation pump has alwayshadas an integral unit, or as a closely attached-element, a vapor generating boiler. Each pump in other words had its own boiler. It was common practice to place a pump at each seat of thevacuum operations. The

pumps seldom required heat. energy in excess 01' a fraction of lhorsepower; Application of heat to a large number of small pump boilers pumping apparatus and process in which a plurality of jets is actuatedby vapors generated in a boiler operating onefllcient principles. A still further object is to provide an improved high vacuum pumping system utilizing vapor-operated ejector pumps (including condensation pumps). Other objects will appear'hereinafter.

These and, other objects are accomplished by my invention which includes a high vacuum producing system comprising a plurality of ejector pumps supplied with vapors of a relatively stable low vapor pressure organic substance by a common boiler located a substantial distance from the ejector pumps, the actuating organic vapors thus being conducted in a conduit over a substantial "distance from the boiler to the ejector pumps. I

In the accompanying drawing wherein like numbers refer to like parts,

Fig. 1 is an elevation partly in section of an improved pumping system embodying the principles of my invention;

Fig. 2 is an elevation partly in section of a modified valve for controlling flow of actuating vapors to the ejector pumps and;

Fig. 3 is another modification of a valve for controlling flow of actuating vapor to the ejector pumps.

Referring to Fig. 1, numeral 5 designates a rectangularlyshaped furnace constructed of suitheating tubes l0 and liquid I2 serving as a source of organic vapors. Numeral l4 designates a gas burner supplied with combustible gas through conduit 16 and diaphragm valve 18. Nu

meral 28 designates a conduit leading from the inside of boiler l2, to diaphragm valve I8. Numeral 22 designates a spring and numeral 24 a wing nut by which the opening and closing of diaphragm valve I 8 can be varied and controlled. Numeral 26 designates a chimney for furnace 6.

To the upper part of boiler 8 is connected a relatively wide aperture conduit 28iwhich serves to convey vapors to a plurality. of distant ejector pumps 38 by way of..-conduit 82 and valves 34. Each ejector pump 88 is provided with a high vacuum or intake conduit 86, ajet nozzle 38, exhaust conduit 48 leading to a backing pump (not shown) and a withdrawal conduit 42 for removal of spent or used actuating fluid. These conduits 42 connect to a common header 44 which leads. to the intake of return pump 46. The exhaust side of pump 46 connects to conduit 48 which terminates in boiler 8 after forming a heat recovery coil 58 in chimney 25.

Numeral 52 designates a conduit connected to the high vacuum side of the ejector pumps and to one side of a diaphragm actuated piston or bellows 54, the piston of which connects to the actuating crank 56 of valve 34.

Referring to Fig. 2 numeral. 56 designates an actuating crank for valve member 58. Numeral 60 designates a shaft connected to a solenoid opand open or close valve member 58. The construction of valve member 84 shown in Fig. 1 is substantially the same as that shown in Fig. 2 except that the valve in Fig. 1 is pneumatically o erated by diaphragm 54 whereas the valve illustrated in Fig. 2 is electrically operated.

Referring to Fig. 3, numeral 68 designates a spherical member suspended in the position shown by three internal projections 68. Numeral I8 designates a valve seat against which sphere 66 is thrown under certain conditions tobe inafterexplained.

In operatingthe apparatus illustrated in Fig. 1 the boiler I2 is filled with an organic pump fluid to the approximate height indicated. Burner I4 is put into operation and valve i8 is adjusted by means of wing nut 24 to maintain a pressure of any desired predetermined value in the boiler l2. Diaphragm valve I 8 is so constructed that the here'- be made to turn the burner i4 off when the pres-,

sure exceeds a certain value and turn the burner on when the pressure in boiler 12 falls below a certain value. Vapors thus generated in boiler l2 and automatically maintained at a desired pressure are conveyed through well insulated conduit 28 to the various ejectors 30. These electors are so constructed that they are automatically actuated by vapors from conduit 28 when backing pumps connected to conduit 40 are put into operation. Thus, when the pressure in conduit 40 is reduced by the backing pump the reduced pressure prevails throughout the system, including conduit 36 which leads to the receptacle being evacuated. This reduced pressure exerts its effect through conduit 52 and actuates diaphragm and piston 54. This reduction in'pressure causes movement of crank 56 of valve 34 to open position. Vapors under pressure then pass at high velocity through valve 34 and jet nozzle 38. Gases in the system to be evacuated are thus drawn through conduit 36 into the jet and are forced into the high pressure end of the pump and are withdrawn by the backing pump through conduit 40. The diffuser tubes of the ejector pumps indicated by the numeral 30 are air cooled so that the organic pump fluid vapors are condensed. The condensate flows by gravity into conduit 42 thence into pump 46 and is returned by way of conduit 48 to boiler 8. Any unrecovered heat of combustion passing up the chimney or stack 26, comes into contact with the return liquid in conduit 50 and the heat is thus taken up and prevented from being wasted.

In many cases a backing pump would be unnecessary. Also in many cases it is not advisable to have automatic operation. In such cases it is valve is electrically opened by energizing coil 64.

The valve automatically returns to its closed position when the electricity is cut off. This enables remote control of the pumps. With this construction the electrically operated shut-01f could be actuated by an operator at a desk where a suitable pressure-indicating device would be mounted to indicate when the pump should be actuated 'or shut off. The construction shown in Fig. 2 also permits automatic actuation. Thus,

when the operation of the electors stopped, i. e.. by allowing the pressure therein to rise, the inrush of ga from the atmosphere throws sphere 68 against seat 10. This automatically cuts off the flow of vaporsto the ejector nozzle 38. In this modification it is obvious that the pressure in boiler 8 and conduit 28 must be below atmospheric to enable closing of the valve by the atmosphere.

In many cases it is desirable to operate boiler a and conduit 28 so that the pressure of the vapors therein is approximately atmospheric pressure. This has many advantages among which are the avoidance of leakage of the vapors into the atmosphere, as well as avoidance of leakage of air into the system. Also, the valve 34, boiler 8 and conduit l2 need not be'constructed with so much care as regards weight and strength of materials, leaks, etc. It is also convenient due to the fact that the atmosphere can be used to actuate the automatic controls maintaining the atmospheric pressure in the boiler.

One of the essential features of my invention is the application of these principles to relatively stable, low-vapor pressure organic pump fluids. These substances are of a peculiar nature, condensing easily and being as a class unstable from a thermal standpoint as compared with substances such as mercury or steam. I prefer to utilize relatively stable organic substances which are 30 substantially"free of constituents having a vapor pressure above about 4.0 mm. or below about 1x mm. at room temperature. However, organic substances somewhat above and below these values can be used.

' While I prefer to employ hydrocarbons as activating pump fluids because of their availability and low cost, other substances can be used with complete satisfaction. Examples are: trichlor- V benzene, Dow Therm," (a mixture of diphenyl 40 and diphenyl oxide), ethers such as"Cellosolve,"

dimethyl phthalate and furfural. Hydrocarbon actuating pump fluids can be obtained from petroleum by distillation to segregate fractions having various desired vapor pressure ranges. 45 Satisfactory pump fluids can be easily obtained by distillation of various hydrocarbon fractions on the market having distillation temperatures and vapor pressures the same as or intermediate SAE 50 lubricating oil and kerosene. The following table indicates the characteristics of specific preferred types of hydrocarbon pump fluids, and their mode of use for best results in the evacuating system described herein.

the; coil 64 could be connected to a sensitive 65 monometer which would be actuated by a reduction in pressure in conduit 52 due to starting of the backing pumps as explained in connection with Fig. 1. Reduction of pressure in the sensitive monometer would cause the coil 64 to be energized. Elevation of the pressure to normal would cut off the electricity as a result of change in the monometer. Another alternative type of valve is shown in Fig. 3 sphere 66 being in the position shown during operation of the ejec l's- 75 Wrtain Pressure p from he oiler t the As source of the above oils I have used:

A-50Wwhite oil B-Winter grade crank case oil (10W) C--Light processing oil D-Spindle oil E-Ice machine oil F-Fuel 011 No. 2

G-Fuel oil No. 1.

It will be realized that there always will be ejector pumps and that this will necessitate some what higher boiler pressures than the above if the system is extensive or improperly insulated. This can be. minimized by eflicient insulation and wide aperture vapor conduits. The vaporgmay partially condense in which case it is desirable toof any type although tubular type boilers are preferred because of their eflicienoy. The boiler can be heated in any desired way but my invention enables, for the first time, theeflicient vaporization of ejector pump organic working fluid by means of cheap fuels such as coal or other combustible materials. The vapors are piped from the remotely situated boiler in large pipes according to advanced power plant practice around many floors of a large factory or laboratory to the ejector pumps as described. It iscontemplated that a multi-horse power installation will thus bring the technology of high vacuum organic vapor actuated pumps to industrial use on a scale never heretofore contemplated.

What I claim is:

1. A high vacuum pumping system comprising in combination a plurality of vapor-operated ejector pumps, a tube type boiler containing a,

relatively stable low vapor pressure organic fluid, means ofiering little resistance to flow of vapors for conveying vapors generated in the boiler to the ejector pumps without substantial'drop' in temperature, means for returning used and spent fluid from the ejector pumps to the boiler and means for heating the boiler said boiler being positioned at a point remote from the ejector pumps.

2. A high vacuum pumping system comprising in combination a plurality of vapor-operated ejector pumps, a boiler containing a relatively stable low vapor pressure organic fluid, means ofiering little resistance to flow of vapors for conveying vapors generated in the boiler to the ejector pumps, means responsive to a reduction or increase in amount of vapors in the boiler or vapor conveying means for maintaining the vapors in the boiler and vapor conveying mean-s at a pressure suflicient to actuate the ejector pumps means for returning used and spent fluid from the ejector pumps to the boiler, and means for heating the boiler, said boiler being positioned in a separate building and at a point remote from the ejector pumps.

3. A high vacuum pumping system comprising in combination a plurality of vapor-operated ejector pumps, a boiler containing a relatively stable organic substance which is substantially free of constituents having vapor pressure below about 1X 10- mm. or above about 4 mm, at room temperature, means for conveying vapors generated in the boiler to the ejector pumps, means responsive to a reduction or increase in amount of vapors in the boiler or vapor conveying means for maintaining the vapors in the boiler and vapor conveying means at a pressure suflicient to actu-. ate theejector pumps means for returning used and spent fluid from the ejector pumps to the boiler and means for heating the boiler said boiler being positioned at a point remote from the ejector pumps.

4. A high vacuum pumping system comprising in combination a plurality of vapor-operated ejector pumps, 9. tube type boiler containing a relatively stable organic substance which is substantially tree of constituents having a vapor pressure below about -1 10- mm. or above about 4 mm. at

room temperature, means for. conveying vapors generated in the boiler to the ejector pumps, means for returning used and spent fluid from the ejector pumps to the boiler and means for heating the boiler said boiler being positioned in a separate building and at a point remote from the ejector pumps.

5. A high vacuum pumping system comprising in combination a plurality of vapor-operated ejector pumps, a boiler positioned at a point remote from the ejector pumps and containing a rela-' tively stable low vapor pressure organic substance, means 'for conveying vapors generated in the boiler to the ejector pumps, means for returning used and spent organic substances from the ejector pumps to the boiler, means for heating the boiler, a valve controlling'the flow of vapors to a each ejector pump and means responsive to a reduction or increase of pressure in the ejector pump for repectively opening or closing the valve.

6. A high vacuum pumping system comprising in combination a plurality of vapor-operated ejector pumps a boiler positioned at a point remote from the ejector pumps and containing a relatively stable organic substance substantially free oimaterials having a' vaporpressure at room tom.

perature below about 1 l0- mm. and above about 4 mm. means for conveying vapors generated in the boiler to the ejector pumps means responsive to a reduction or increase in amount of vapors in the boiler or vapor conveying means for maintaining the vapors in the boiler and vapor .conveying means at a pressure suflicient to actuate the ejectorpumps means for returning used and spent fluid from the ejector pumps to the boiler, means for heating the boiler, a valve controlling the flow of vapors to each ejector pump and means responsive to a reduction or increase of pres-sure in the ejector pump for respectively opening or closing the valve. 7. A high vacuum pumping system comprising in combination aplurality of vapor-operated ejector pumps a boiler positioned at a point remote from the ejector pumps and containing a relatively stable low vapor pressure organic substance,

means for conveying vapors generated in the boiler to the ejector pumps means responsive to a reduction or increase in amount of vapors in the boiler or vapor conveying means for maintaining the vapors in the boiler and vapor conveying means at a pressure sufiicient to actuate the ejector pumps means for returning used and spent organic substance from the ejector pumps to the boiler means for heating the boiler, means for automatically maintaining the pressure in the boiler at approximately atmospheric pressure, a

valve controlling the flow of vapors to each ejecspent fluid to the boiler, said boiler being positioned at a point remote from the ejector pumps.

9. A high vacuum pumping system comprising in combination a plurality of ejector pumps, a boiler containing a relatively stable low vapor pressure organic substance, means for'heating the boiler with a combustible substance, means for conveying working vapors from the boiler to the ejector pumps, means responsive to a reduc-- tion or increase in amount of vapors in the boiler, or vaporconveying means for maintaining the vapors in the boiler and vapor conveying means.

at a pressure sufficient to actuate the ejector pumps and means for returning the used and spent organic substance to the boiler, said boiler being positioned at a point remote from the ejector pumps.

10. A process of evacuating by means of a plurality of ejector pumps connected to a common source of actuating vapor which comprises generating vapors of a relatively stable low vapor pressure organic substance in a boiler at a pressure sufllcient to actuate the ejector pumps, conveying these vapors through a conduit to the ejector pumps, and starting or stopping the pumping action by starting or stopping the flow of actuating vapors to the ejector pumps while maintaining the pressure of the vapors in the boiler and conduit at actuating pressure during both pumping and non-pumping periods.

11. A process of evacuating by means of a plurality of ejector pumps connected to a common source of actuating vapor which comprises generating vapors of a relatively stable low vapor pressure organic substance in a boiler at a pressure sufficient to actuate the ejector pumps, conveying .these vapors a substantial distance through a conduit to the ejector pumps, and starting or stopping the pumping action by starting or stopping the flow of actuating vapors to the ejector pumps while maintaining the pressure of the vapors in the boiler and conduit at actuating pressures during both pumping and non-pumping periods.

12. A .process of evacuating by means of an ejector pump connected to a source of actuating vapor which comprises generating vapors of a relatively stable low vapor pressure organic substance in a boiler at a pressure suiflcient to actuate the ejector pump, conveying these vapors a substantial distance/through a conduit to the working fluid inlet of the ejector pump, and starting or. stopping the pumping action by starting or stopping the flow of actuating vapors to the ejector pump while maintaining the pressure of the vapors in the boiler and conduit at actuating pressures during both pumping and non-pumping periods.

13. A process of evalcuating by means of a plurality or ejector pumps connected to a common source of actuating vapor which comprises generating vapors of a relatively stable low vapor pressure organic substance substantially free of constituents having a vapor pressure below about 1 10- mm. or above about 4 mm. in a vapor generator at a pressure sumcient to actuate the ejector pumps, conveying these vapors a substantial distance through a conduit to the ejector pumps, and starting or stopping the flow of actuating vapors to the ejector pumps while maintaining the pressure of the vapors in the vapor generator and conduit at actuating pressures during both pumping and non-pumping periods.

14. A process of evacuating by means of a plurality of ejector pumps connected to a common source of actuating vapor positioned a substantial distance therefrom which comprises maintaining vapors of'a relatively stable low vapor pressure organic substance in the vapor source at a vapor pressure closely approximating atmospheric pressure whereby leakage of working vapors from or of air into the vapor source is substantially avoided.

15. A process of evacuating by means of a plu- 

